Ink, ink set, ink cartridge, recording unit, image recording process and image recording apparatus

Abstract

Disclosed herein is an ink comprising a pigment and a resin encapsulating a coloring material. The ink can provide an image high in optical density and excellent in rub-off resistance, water fastness and resistance to line marker, and exhibits excellent ejection stability from a recording head when used in ink-jet recording.

What is claimed is:  
     
       1. An aqueous ink for an ink-jet printing process comprising: 
       a self-dispersing pigment and a resin encapsulating a coloring material, both of which are dispersed in an aqueous medium such that the total amount of the solid concentration of the self-dispersing pigment and the resin encapsulating a coloring material is 8 percent by weight based on the total weight of the ink,  
       the resin encapsulating the coloring material being contained in a sufficient amount to provide rub-resistance to an image produced with the ink,  
       wherein the ink provides an ink jet recorded image with a certain optical density that is equivalent to that produced with an ink containing the self-dispersing pigment as a sole colorant at the solid concentration of 8 percent, and wherein the encapsulated coloring material is an oil-soluble dye or a water-insoluble pigment.  
     
     
       2. The ink according to  claim 1 , wherein the self-dispersing pigment is a self-dispersing carbon black to the surface of which at least one hydrophilic group is bonded directly or through another atomic group. 
     
     
       3. The ink according to  claim 2 , wherein the hydrophilic group is anionic. 
     
     
       4. The ink according to  claim 3 , wherein the resin encapsulating a coloring material has an anionic hydrophilic group at the surface thereof. 
     
     
       5. The ink according to  claim 2 , wherein the hydrophilic group is cationic. 
     
     
       6. The ink according to  claim 5 , wherein the resin encapsulating a coloring material has a cationic hydrophilic group at the surface thereof. 
     
     
       7. The ink according to  claim 2 , further comprising a pigment dispersant having an anionic hydrophilic group when the hydrophilic group bonded to the surface of the self-dispersing carbon black is anionic. 
     
     
       8. The ink according to  claim 2 , further comprising a pigment dispersant having a cationic hydrophilic group when the hydrophilic group bonded to the surface of the self-dispersing carbon black is cationic. 
     
     
       9. An image recording process comprising the step of applying at least two color inks to a recording medium using an ink-jet method to form a multi-color image, wherein one ink is an ink according to  claim 5  or  8 , and the other ink comprises a compound having an anionic group. 
     
     
       10. An image recording apparatus, comprising: 
       ink containers containing first and second inks respectively, and a recording head for ejecting the respective inks, wherein the first ink is an ink according to  claim 5  or  8 , and the second ink is an anionic ink.  
     
     
       11. The ink according to  claim 1 , further comprising a pigment dispersant. 
     
     
       12. The ink, according to  claim 1 , wherein the pigment and the coloring material have the same color. 
     
     
       13. The ink according to  claim 1 , wherein the coloring material is encapsulated in a microcapsule made of the resin. 
     
     
       14. An ink cartridge, comprising an ink container containing an ink according to  claim 1 . 
     
     
       15. A recording unit, comprising: 
       an ink container containing an ink according to  claim 1 ,  
       a recording head, and  
       means for feeding the ink from the ink container to the recording head.  
     
     
       16. An ink set comprising a first ink and a second ink in combination, wherein the first ink is an ink according to  claim 1 , and each of the first and second inks has a color selected from the group consisting of yellow, magenta, cyan, black, red, green and blue. 
     
     
       17. An image recording process, comprising the step of applying an ink according to  claim 1  to a recording medium by an ink-jet process. 
     
     
       18. An image recording apparatus, comprising: 
       an ink container containing an ink according to  claim 1 ; and  
       an ink-jet head for ejecting the ink.